Color imaging charge-coupled array with multiple photosensitive regions

ABSTRACT

A photosensitive apparatus comprises a single crystal structure, wherein different regions of the structure are of different compositions. A first photosensitive region comprises a material adapted to generate electron-hole pairs in an area thereof exposed to light within a predetermined first range of wavelength, and a second photosensitive region, comprises a material adapted to generate electron-hole pairs in an area thereof exposed to light within a predetermined second range of wavelength different from the first range of wavelength. 
     This application incorporates by reference a previously-filed application, Ser. No. 07/973,811, entitled &#34;Color Imaging Charge-Coupled Array with Photosensitive Layers in Potential Wells,&#34; filed Nov. 5, 1992, and having the same inventor and assignee as the present application.

The present invention relates to a photosensitive device, preferably inthe form of a charge-coupled array (CCD), having a multi-regionstructure for imaging full-color images.

Charge-coupled arrays (CCD's) are generally defined as layeredstructures for the selective retention of charge in specific areasthereof, wherein the structure itself may serve as a shift register forselective serial readout of data in the form of the charged areas.Discrete areas within the CCD are caused to store charge because theelectrical potential is lower in the particular area holding the chargethan in the surrounding material. When it is desired to read out thecharges as a serial signal, the charge in each area can be transferredfrom one area to its neighbor by suitably changing the potential on itand its neighbor so that charge flows from one area to the next. Byapplying charges to a linear series of electrodes along the array,typically with some time period of overlap of charging adjacentelectrodes, individual charge packets can be caused to move along theCCD. The system for transferring discrete charge packets from one areato the next until the charges are read out as a serial signal iscolloquially known as the "bucket-brigade" method of readout. An earlypatent describing the shift register operation of a CCD is U.S. Pat. No.3,971,003.

One special type of CCD is the photosensitive, or "imaging," CCD,wherein discrete areas of charge, which may be read out as serialsignals, are initially created in the CCD by the imagewise focusing oflight onto the structure. With certain materials, such as aluminum,gallium, and arsenic compounds and combinations in an ordered crystalstructure, photons focused on the material will create electron-holepairs in areas corresponding to the distribution of light in the image.Thus, the CCD forms a linear array of photosensors upon which narrowsections of an image can be recorded, while the CCD can output datarelated to the image. Such CCD's, particularly monochrome CCD's, are incommon use in facsimile machines, digital copiers, and other scanners.One typical example of such an imaging CCD is shown in U.S. Pat. No.4,658,278.

In digital scanning equipment, such as facsimile machines, digitalcopiers, or any apparatus in which a hard-copy original is read and thesignals converted to digital data, a common arrangement is to provide aseries of very small photodetectors and cause the photodetectors to moverelative to the hard-copy original. These photodetectors are arranged ina linear array at a spacing typically on the order of 200 to 400detectors per inch, and this linear array is moved across the originalso that the photodetectors are disposed to the original one line at atime. Most scanners and facsimile machines currently in common use aremonochrome, that is, insensitive to the colors on a hard-copy original,and therefore most imaging CCD's are sensitive merely to gradations ofdark and light. For color scanning devices, one common arrangement is toselectively interpose one or another color filter between the hard-copyoriginal and the photodetectors, and then scan the hard-copy original anumber of times, each time with a different color filter, thus ending upwith a set of discrete "batches" of data, each batch representing theseparation of one color from the document. In order to providesubsequent display or printout, the separate batches are superimposed toreassemble the full-color document. Another known technique is toprovide three separate linear arrays, typically arranged in parallel andin close proximity to one another, each separate linear array having asmall color filter associated therewith. Despite the color filterassociated with each array, the underlying photosensitive structure ofeach such array is typically identical; this system merely controls thenature of light going into each of the respective linear arrays.However, there has been attempts in the past to create photosensitivestructures for use in CCD's which are inherently sensitive to variouscolors.

U.S. Pat. No. 4,383,269 discloses a photodetector having an energy bandstructure which causes one type of charge carrier, either an electron ora proton, to ionize at a faster rate than the other type of chargecarrier. The photodetector is preferably formed from semiconductorsincluding gallium, aluminum, arsenic, and phosphides.

U.S. Pat. No. 4,432,017 discloses a high density imaging CCD having abilinear array of photosites on a single integrated circuit chip. Thephotosites are offset relative to each other in two rows and coupled toa respective pair of storage registers and shift registers.

U.S. Pat. No. 4,847,489 discloses a superlattice photodetectorarrangement having a plurality of photosensitive detector elements, eachelement having a multi-layer structure of alternating positively andnegatively doped photosensitive semiconductor material. Controlelectrodes are arranged vertically with respect to the semiconductorlayers, and adapted to receive a control voltage in order to control thespectral light sensitivity thereof.

U.S. Pat. No. 5,138,416 discloses a multi-layer color photosensitiveelement having different layers, each sensitive to a different primarycolor, and differing primarily by composition. Charge is collected fromthe various layers according to an amount of time for light of variouscolors to travel through the layers.

Tokumitsu et al., "Photo-metalorganic Molecular Beam Epitaxy: A NewEpitaxial Growth Technique," Journal of Vacuum Science and TechnologyVol. 7, No. 3, May/June 1989, at 706-709, discloses a technique formaking photosensitive crystal structures with specific arrangements ofcompositions.

In accordance with the present invention, there is provided aphotosensitive apparatus comprising a crystal structure having a firstphotosensitive region, comprising a material adapted to generateelectron-hole pairs in an area thereof exposed to light within apredetermined first range of wavelength, and a second photosensitiveregion substantially coplanar with the first photosensitive region,comprising a material adapted to generate electron-hole pairs in an areathereof exposed to light within a predetermined second range ofwavelength different from the first range of wavelength.

In the drawings:

FIG. 1 is a schematic perspective view showing a CCD made according tothe present invention;

FIG. 2 is a sectional elevational view taken in the direction of thearrow, along the line 2--2 of the CCD shown in FIG. 1;

FIG. 3 is a sectional elevational view taken in the direction of thearrows along the line 3--3 of the CCD shown in FIG. 1;

FIG. 4 is a partially schematic or planar view of a differencing systemfor sorting signals output by a CCD made according to the presentinvention; and

FIG. 5 is a schematic elevational view of a scanning apparatus in whicha CCD according to the present invention would be suitable for use.

FIG. 1 shows a photosensitive device in the form of a CCD for full-colorscanning, according to the present invention. The photosensitive device,generally indicated as 10, is in the form of a member having a singlecrystal structure; that is, the entire photosensitive device 10 ispreferably made from a single crystal structure continuous throughoutthe device, as opposed to comprising separate crystal structures createdseparately and then abutted to each other. Although the entire member ismade from a single crystal structure, as will be explained below, thecomposition of the structure will vary at different portions of thephotosensitive device. Further, the device 10 may itself be a portion ofa larger member, such as a wafer extending beyond the boundaries of thedevice shown in FIG. 1.

In order to be useful for a scanning apparatus, the photosensitivedevice 10 is of a generally elongated shape, and is generally dividedalong its length into a photosensitive portion 12 and opaque portion 14.The top surface of photosensitive portion 12 is divided into any numberof regions in the form of parallel rows, such as shown as B, G, R, andK, which, as will be explained in detail below, correspond to blue,green, red and white (for a black image) light respectively. Inaddition, the opaque portion 14, which is insensitive to light, isfunctionally divided into rows a, b, c, and d. This arrangement of rowsin both the photosensitive portion 12 and opaque portion 14 can be seenclearly in the cross-sectional view of FIG. 2.

Each row B, G, R, K and a, b, c, d of the device 10 is, in its otherdimension, divided into pixel sections numbered in FIG. 1 as 1, 2, 3 . .. n. These pixel sections correspond to picture elements (pixels) bywhich scanned-in images from the exposure of the photosensitive device10 is converted into image data. The intersection of the pixel sectionswith the rows in portion 12 form individual photosites, such that eachpixel in the array has assigned to it four photosites (one for eachcolor) in portion 12, and, in the corresponding portion 14, four "placeholders" which operate as shift registers, in a manner which will beexplained in detail below. A typical spacing of such pixel sections in afull-width one-to-one scanning apparatus would be 200 to 400 pixelsections per inch. However, as many scanning apparatus employ reductionlenses, the actual size of the pixel sections may be as small as 600 to800 per inch. Generally, reduction lenses are employed in conjunctionwith CCDs because there may be cost advantages to having aphotosensitive device which is smaller in absolute terms, even if ahigher resolution on the devices is required. The individual pixelsections for each row B, G, R, K and a, b, c, d are aligned for eachrow, as can be seen in the cross-section of FIG. 3, which could be saidto represent the pixel sections in any row.

As can be clearly seen in the cross-sectional views of FIGS. 2 and 3,each pixel section in photosensitive portion 12 and each section a, b,c, d in opaque portion 14 has associated therewith an electrode 20.General techniques are known in the art for providing such electrodes 20to individual pixel sections and other portions of a CCD wherebyspecific sections may be addressed without interfering with thetransmission of light to any particular section as needed. (However, inthe illustrated embodiment, opaque portion 14 is not intended to receivelight, and thus no provision for allowing the transmission of lightthereon will be necessary.) These various electrodes 20 are selectablyaddressed in sequences which would be familiar to one skilled in theart, whereby charge packets within various sections of the device 10 maybe caused to migrate as desired from one area associated with aparticular electrode 20, to an area associated with an adjacentelectrode 20.

When the device 10 is exposed to light, particularly in image-wisefashion as would occur in the course of scanning a hard-copy originaldocument, a "slice" of the image will be focused on the photosensitiveportion 12 of device 10, and the photosites in the different pixelsections will receive different intensities of different color lightdepending on the image and the placement of the particular pixelsection. For a full-color original, within each pixel section 1, 2, 3 .. . n, different color sections B, G, R, K will respectively besensitive to a particular component color (respectively, blue, green,red, and white) of the particular pixel associated with each column ofpixel sections 1, 2, 3, . . . n. Thus, for the endmost pixel 1, theremay for example be a purple area in the hard-copy original, causingcharge activity in the blue and red sections of the pixel section 1 torespective extents dependent on the actual hue of the original in thatpixel area. (Although the primary colors are given here, as is typicalin any full-color scanning system, the system may be designed for anykind of color separation as desired. Charge packets in the K zone relateto white light, and use may be made of this "gray" signal as desired inan image-processing system.)

In photosensitive imaging CCD's or other photosensitive devices, theenergy associated with light will act to create specific quantities ofelectron-hole pairs. Either the electron or the hole of these createdpairs may be retained to form "charge packets," in the photosensitiveregions of the structure. Thus, the corresponding regions sensitive toindividual primary colors in The multi-region structure of CCD 10 will,upon exposure to light, be energized (that is, charge packets of acertain charge magnitude will be created) to the extent that individualprimary colors are present in the light in the particular pixel. In thisway, a color separation is possible for each pixel.

Once the CCD has been exposed, as in part of a cycle wherein one of aseries of line images forming a complete image are exposed onto thelinear array of the CCD in a scanner, there begins a readout step inwhich the charge values in the photosensitive regions of the CCD areread out in the familiar "bucket-brigade" fashion to form a series ofsignals at the end of the CCD. In the preferred embodiment of thepresent invention, the readout of data for each color within each pixelsection is a two-part process. First, the individual charge packets foreach color within each pixel section are shifted first into the opaqueportion 14 of the device 10. Thus, by applications of suitable chargesfor suitable amounts of time to the electrodes associated with the pixelsection, the charge packets created by the exposure of light on thephotosites in rows B, G, R, K are shifted into sections a, b, c, drespectively. In this way, the four possible charge packets (assumingthere is an input for each of the four colors in that particular pixelsection at that time) are shifted sequentially into the opaque section.This induced migration of charged packets from the photosensitiveportion 12 to the opaque portion 14 for each pixel section in effect"clears" the photosensitive portion 12 so that another exposure cycle ofphotosensitive portion 12 may begin while the image data for the pixelsection in the previous exposure is temporarily stored in opaque portion14 for that pixel section.

In the second part of the read out process, the charge packets in rowsa, b, c, d of opaque portion 14 are read out sequentially in parallelstreams across the rows; that is, the charge packets in row a are movedin CCD "bucket-brigade" fashion across the device 10 from pixel section1, to 2, to 3, etc. This sequential read out, induced by the properapplication of suitable charges to the electrodes 20 associated with thesections of opaque portion 14, is familiar in the art of CCD shiftregisters. At the read out end of the device 10, as the charge packetsassociated with image data are fed out in parallel streams, there iscreated a sequence of charge values (based on the magnitude of theindividual charge packets) which will form parallel serial streams ofimage data, each stream being representative of one color orwhite/black. Thus, the two-part read out process of the preferredembodiment of the claimed invention first shifts all the charge packetsinto opaque portion 14 to clear the photosensitive portion 12, and thenthe charge packets are downloaded sequentially from the end of theopaque section.

Of course, it is possible that for a more simple form of read out fromthe photosites in rows B, G, R, K in photosensitive portion 12, thatserial readout across the columns can be performed directly from theends of the respective rows or pixel sections in photosensitive portion12.

In the illustrated embodiment, the series of electrodes 20 may beconnected to an external circuit (not shown) to apply appropriatevoltages to discrete areas of the array; thus the electrodes enable theshifting of charge packets across the array in various directions asneeded. In the case of the multicolor CCD of the present invention, eachcolumn 1, 2, 3 . . . n of pixel sections in the photosensitive devicewill act as an independent CCD and the readout step will result inparallel data streams, each data stream representing one color of therow of pixels. This bucket-brigade technique generally consists ofapplying a series of potentials to the electrodes 20 in a sequence sothat, by decreasing the potential to one side of a given pixel, thecharge packet in one particular pixel section of the CCD will move overby the length of one pixel. This process is repeated, as is known in theart, until all of the image data, in the form of discrete charge packetsassociated with each pixel, is read out at the end of the CCD.

In constructing a photosensitive device such as 10 of a single crystalstructure, an obvious concern is providing individual sections in thephotosensitive area 12 which are inherently sensitive to specificwavelength of light. By having specific regions of the device inherentlysensitive to specific wavelength ranges, the usual necessity forproviding glass or plastic color filters of one type or another isavoided; ability to avoid such filters will increase the sensitivity,and thus the possible speed, of such a scanning device. According to thepresent invention, there is provided a single crystal structure wherein,although the structure is continuous throughout the member, thecomposition of the structure in various regions of the member isslightly different. It is known that certain crystal compositions areable to create charge packets when exposed to light of specificwavelength ranges.

In order to create the desired structure of regions sensitive toparticular desired primary colors, there are many possible directband-gap materials available, such as (Al_(x) Ga_(1-x))_(y) In_(1-y) As.It is also possible to use indirect gap materials for the photosensitiveregions, such as ordered crystals of Al_(x) Ga_(1-x) As. The proportionof aluminum to gallium in this ordered crystal structure (given as x)may be varied for sensitivity to a particular energy associated with adesired wavelength for a given region. The use of indirect gap materialsis possible because there is a large increase in absorption for energiesat and above the material's direct gap. The small amount of absorptionbelow the direct gap can be corrected for once the signals are read outand converted to digital form. With these materials, a given compositionwill be sensitive, generally, to a certain wavelength and shorterwavelengths, in a range bounded only at one end. Thus, when preparing astructure for absorption of a specific set of wavelengths, differencingmeans, as will be described in detail below, are typically required tosort out signals representative of light of wavelength ranges bounded attwo ends.

In brief, the best known proportions of aluminum to gallium are shown inthe table below for a desired wavelength sensitivity:

In a four-color embodiment of the present invention, such as that shownin FIGS. 1-3, one possible arrangement of the compositions of therespective sections K, R, G, and B would be as follows: for the Kregion, sensitive to white light (the entire visible spectrum), thevalue x=0.3; for the R section (sensitive to red and all shorterwavelengths, such as green and blue), x=0.45; for the G section(sensitive to green and all shorter wavelengths, particularly blue),x=0.75; and for the B region (sensitive to blue and all shorter wavelengths in the visible spectrum), x=0.85. Of

    ______________________________________                                        Al.sub.X Ga.sub.1-X AS                                                                    Direct gap            Color                                       X =         eV        λ(μm)                                                                           (approx.)                                   ______________________________________                                        0.45        2         .62         red                                         0.6         2.2       .56         yellow                                      0.75        2.4       .52         green                                       0.85        2.6       .48         blue                                        0.9         2.8       .44         violet                                      ______________________________________                                    

course, the precise compositions of the respective sections, relative tothe precise desired colors to be detected, will be a matter of designchoice for a particular apparatus. As mentioned above, because thenature of the crystal structure of the preferred embodiment of thepresent invention causes a particular region to be sensitive to aparticular color and all shorter wavelengths, there is typicallyrequired means for separating out the signals associated with variousregions of the device 10 so that the output signals relate to specificdouble-bounded ranges of the color spectrum.

Opaque portion 14 of device 10 is not intended to be exposed to light,but it is preferably formed from the same crystal structure as thephotosensitive portion 12. The composition of opaque portion 14 shouldbe such that charge packets may be able to pass therethrough in acontrollable manner, and so in the illustrated embodiment the value of xshould be selected to optimize the passage of charge packetstherethrough.

FIG. 4 is a partially-schematic view of the rudiments of differencingmeans by which the charge packets associated with different rows in theopaque portion 14, which have been transferred from respective rows inphotosensitive portion 12, are sorted to yield signals relating todouble-bounded wavelength ranges. Assuming in this embodiment that thecharge packets created in rows B, G, R, and K are transferred seriatimto rows a, b, c, and d respectively in opaque portion 14, it will benoted that because of the cumulative nature of wavelength sensitivity ofthe various photosensitive regions, the charge packets in row b, whichwere transferred from row G, are related to the amount of light of greenwavelength and shorter, particularly blue light; therefore, the chargepacket in row b is representative of green light plus blue light.Similarly, the charge packets in row c, which were transferred from rowR, were created by light of red wavelengths and shorter, in effect, redplus green plus blue. The charge packets in row a, originally from rowB, are in this example primarily blue because blue is the shortestwavelength light to which the system is sensitive. Further, the chargepackets in row d, which were transferred from the black/white row K,were created by the action of light from the entire visible spectrum.

Because the charge packets in row a, relating to blue light exclusively,and the charge packets in row d, wherein the actual color of the lightis largely immaterial, do not contain charge relating to light not ofinterest to that row, the charge packets in rows d and a may beconverted directly into (typically digital) signals for use by animage-processing system. The charge packets in rows c and b, however,contain, in addition to charge packets relating to the red and greenlight respectively, extra charge packets relating to other colors.Charge related to superfluous colors in rows b and c must, in effect, beseparated out, leaving only the amount of charge relating to the colorof interest. For this separating purpose, differencing means, such asthe amplifiers shown as 30 and 32, are employed. In the case of theamplifier for the green light signal, as can be seen, the charge packetsfrom row b, representative of green and blue light, have subtracted fromthem the charge relating to blue light only, which can be determined bythe charge in row a for the same pixel. Thus, the subtraction(G+B)-(B)=G is performed. Similarly, the charge in row c may havesubtracted therefrom the green plus blue charge from row b and thesubtraction (R+G+B)-(G+B)=R is performed. This subtraction may beperformed by any electronic means familiar in the art, such asoperational amplifiers or digital systems.

Although it was mentioned above that one key advantage of thephotosensitive device of the present invention is that it obviates theneed for providing additional light filters, for example, of translucentplastic or glass, in combination with the photosensitive device, it maybe possible that, for purposes of convenience of design of an apparatus,such light filters may be employed. The combination of light filterswith various photosensitive regions of the photosensitive device 10 maybe used to "fine-tune" the color acuity of a system, or may be used toeliminate the need for differencing means as shown in FIG. 4. The lightfilter may be applied directly to, or in close proximity to, individualwavelength-sensitive regions of the device 10, or alternately there maybe provided in a scanner means for disposing one of a plurality of suchfilters as needed between the device 10 and the hard-copy original, forexample, in a multi-pass scanning system.

FIG. 5 is a simplified elevational view showing the rudiments of ascanning device for a hard-copy original which may employ aphotosensitive device of the present invention. The scanner 100 includesa pivotable top cover 102 under which a hard-copy original HC may beplaced for scanning. Inside the scanner 100 is a carriage 104, adaptedby a motor (not shown) to move along a track 106 to scan across the hardcopy original C. Within the scanner 104 are optical elements such asmirror 108 and reducing lenses 110, which cause light from a lightsource 112 caused to reflect from the hard-copy original to be directedto a photosensitive device 10, such as that shown in FIG. 1. Thereducing lenses 110 may be used to allow for a device 10 which issmaller than the width of the hard-copy original, or alternately afull-width device 10 may be provided. The full-color outputs from thedevice 10 may be downloaded into a buffer or other circuit elementindicated as 114, to be converted into parallel streams of signals.These parallel streams of signals, one stream for each color, may thenbe sent, as needed, to image processing means 116 for whatever purpose.

There is presently known in the art at least one technique for creationof a unitary member having a single crystal structure, wherein specificregions of the main surface of the member can be provided with aspecific composition while the member as a whole retains a consistentcrystal structure. This preferred technique, known as metalorganicmolecular-beam epitaxy, or MOMBE, is described, for example, inTokumitsu et al., "Photo-metalorganic Molecular Beam Epitaxy: A NewEpitaxial Growth Technique," published in the Journal of Vacuum Scienceand Technology Vol. 7, No. 3, May/June 1989, at 706-709.

Briefly, under this technique, metalorganic compounds or hydridereactant gases are introduced into an ultrahigh vacuum chamber anddirected towards a crystal substrate. The metalorganic compounds areintroduced as molecular beams, as opposed to in a viscous flowcondition. This beam nature makes it possible to switch on and off themolecular beams of the reactant gases abruptly by using shutters. Mostusefully for the present invention, it has been shown that, with theMOMBE technique, ternary and quaternary alloys having more than twogroup-V elements, such as GaAsP and InGaAsP, can be reproducibly grown.Further, photochemical reaction processes can be incorporated in MOMBEto prepare a superlattice structure. It is thought that the preparationof such a superlattice structure can be accomplished by switching on andoff laser irradiation during the process, instead of operating shutters.Alternatively, one of the group-Ill or group-V compounds can be providedusing a metalorganic source and all other species be provided usingsolid molecular-beam epitaxy sources. In this manner the amount of laserintensity can control the rate of decomposition and incorporation ofonly one of the species. The alloy composition grown with the laserirradiation will be different from that grown without the laserirradiation, and through this technique, the composition of the alloyscan be controlled by the laser irradiation. By applying varyingintensities laser irradiation across the surface of the growing film thecomposition can be controlled in an area selective manner. Therefore, itis evident that, using these techniques, the composition of a crystalstructure such as in device 10 can be accurately controlled during thecrystal growth process in such a way the desired compositions of thecrystals are present in the desired positions within the device.Particularly relevant to the preferred embodiment of the presentinvention, Tokumitsu et al. states at 709 that the MOMBE technique canbe used to control the composition of Al_(x) Ga_(1-x) As crystals.

While this invention has been described in conjunction with a specificapparatus, it is evident that many alternatives, modifications, andvariations will be apparent to those skilled in the art. Accordingly, itis intended to embrace all such alternatives, modifications, andvariations as fall within the spirit and broad scope of the appendedclaims.

I claim:
 1. A photosensitive apparatus having a single crystal structure and defining a light-receiving surface, comprising:a first photosensitive region of the light-receiving surface, including a first material generating electron-hole pairs in an area thereof in response to being exposed to light within a predetermined first range of wavelength; a second photosensitive region of the light-receiving surface, including a second material different from said first material, generating electron-hole pairs in an area thereof in response to being exposed to light within a predetermined second range of wavelength different from the first range of wavelength, and a non-photosensitive region, retentive of charge packets in discrete locations thereof, wherein the non-photosensitive region defines a plurality of discrete sub-regions, each sub-region being selectably retentive of a discrete charge packet.
 2. The photosensitive apparatus of claim 1, wherein the sub-regions of the non-photosensitive region are arranged in a two-dimensional array.
 3. The photosensitive apparatus of claim 1, wherein each sub-region includes an electrode associated therewith.
 4. A photosensitive apparatus having a single crystal structure and defining a light-receiving surface, comprising:a first photosensitive region of the light-receiving surface, including a first material generating electron-hole pairs in an area thereof in response to being exposed to light within a predetermined first range of wavelength; a second photosensitive region of the light-receiving surface, including a second material generating electron-hole pairs in an area thereof in response to being exposed to light within a predetermined second range of wavelength different from the first range of wavelength; each photosensitive region defining a plurality of discrete pixel regions, each pixel region being selectably retentive of a discrete charge packet; and a non-photosensitive region, retentive of charge packets in discrete locations thereof, the non-photosensitive region defining a plurality of discrete sub-regions, each sub-region being selectably retentive of a discrete charge packet.
 5. The photosensitive apparatus of claim 4, wherein:the pixel regions are arranged in a first two-dimensional array, and the sub-regions of the non-photosensitive region are arranged in a second two-dimensional array.
 6. The photosensitive apparatus of claim 5, wherein each sub-region and each pixel region includes an electrode associated therewith. 